This invention relates to the delivery of measured quantities of liquid fuel into the induction passage of an internal combustion engine.
The various fuel injection systems currently in use, in internal combustion engines, operate on the basis of a column of liquid between the point of application of the injection force to the fuel and the delivery nozzle. These systems rely on the adding of a metered quantity of fuel to the upstream end of the column to displace an equal quantity of fuel from the nozzle at the downstream end of the column. In order to achieve the required accuracy in the quantity of fuel delivered from the nozzle, the column of fuel must be free of gas, due to its compressible nature.
It is also necessary for the nozzle to be selectively opened and closed to maintain the gas-free state of the column of fuel between successive deliveries, or to ensure sufficient delivery pressure for continuous systems, to maintain the gas-free state of the fuel line.
These selectively openable nozzles are required to be high precision components in order to maintain metering integrity and/or consistent spray characteristics. Hence, manufacturing cost is high and susceptibility to fouling by foreign materials in the fuel is prevalent. Additionally durability is a potential problem due to the frequency of opening of the nozzle for either a pulsed or continuous metering system. (In the latter case, the natural vibrational frequency of a spring-loaded nozzle is excited even though output is nominally continuous.)
U.K. Patent No. 2,023,226 involves continuous injection of a fuel/air mixture into the inlet manifold of an internal combustion engine. Compressed air and fuel are delivered separately to a mixing chamber immediately adjacent the injection nozzle, and the pressure in the mixing chamber actuates the valve in the nozzle to effect injection of the fuel/air mixture to the engine. The mixing chamber in the nozzle incorporates a porous sintered element, but it is believed this feature does not contribute significantly to proper atomization of the fuel. The required atomization is apparently achieved by the pressure drop through the valve, and the consequent sonic velocity. This injection system does not employ a constantly open injection nozzle, nor is the fuel conveyed to the nozzle by individual shots of air.
German Patent No. 314,252 employs a constantly open nozzle and high pressure air to effect injection of fuel through the nozzle. A fuel dispensing surface (grid) is provided between a fuel storage chamber and the delivery nozzle, to assist atomization of the fuel. The disclosure relates to injectors for diesel engines, and it is not disclosed that the high pressure air contributes to atomization of the fuel.
Australian Patent No. 237,354 discloses an injection system wherein a constant supply of fuel is delivered to a constantly open nozzle as a continuous flow. There is no air associated with the conveying of the fuel to the respective nozzles, or the delivery of the fuel from these nozzles.